The invention concerns a photographic copying apparatus having a projection means to image a copy master onto a photosensitive copy material, a photoelectric measuring layout to measure the copy master in a plurality of scanning sections in scanning lines extending over the copy master, and exposure controls combined with the measuring layout and the projection means to determine the quantities of copy light exposing the copy material.
A color copying apparatus of this type is known for example from EP-A-O 312 499. In the case of the color copying apparatus described therein the color extract values essentially controlling the exposure are obtained in a manner such that a line of the copy master comprising numerous individual (imaginary) scanning areas is always exposed and that the light coming from every scanning area of the copy master is resolved by a prism into narrow spectral sections. This light divided into spectral sections impacts a two-dimensional field of photoelectrical transducers arranged in columns and lines. The columns extend parallel to the scanning line on the copy master and the lines are perpendicular to it. A line of the transducer field is correlated with each of the scanning sections of the scanning line on the copy master being exposed and every individual photoreceiver of such a line is correlated with a spectral section of the measuring light from the associated scanning section. The individual lines of the two-dimensional transducer field are located adjacent to each other, in a manner identical with the layout of the associated scanning sections of the illuminated line on the master. The scanning of the individual scanning lines of the copy master takes place sequentially by the stepping advance of the copy master chosen in keeping with the resolution desired.
The simultaneous scanning of a complete scanning line of the master therefore requires a two-dimensional field of photoreceivers: one dimension for the spatial resolution of the line into its individual scanning sections, and the other for the spectral resolution into individual spectral sections. The simultaneous scanning of the entire copy master, i.e. all of the scanning lines, simultaneously is not possible with such a scanning apparatus, as for this another "dimension" of photoreceivers would be required. Consequently, with the copy apparatus of EP-A-O 312 499 the scanning of the individual lines of the copy master must be carried out sequentially, as mentioned above.